Power semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors), etc., are used in power electronics technology. In recent years, it is becoming desirable to use electrical energy even more efficiently, and the development of power electronics technology and power semiconductor elements is becoming even more important for highly-efficient power conversion. Low switching loss, high-speed operation, a wide area of safe operation, and a wider range of breakdown voltages are necessary for such power semiconductor elements.
Among these, the breakdown voltage is important for both the element edge terminal region and the element cell region which determines the breakdown voltage of the element itself. In the element edge terminal region, breakdown may occur due to a locally-high electric field due to the structure of the element edge terminal region. Therefore, the breakdown voltage design of the element edge terminal region also is important; and currently, structures have been proposed such as a VLD (Variation of Lateral Doping) structure, a RESURF structure, a guard ring structure, etc. Further, the reliability is important so that breakdown voltage fluctuation, leakage current increase, etc., do not occur even for the conditions of high temperatures and voltage applications for a long period of time.